There is currently interest within the oil industry in the application of electrokinetic measurements for the evaluation of formations penetrated by wells. Applications of electrokinetic measurements include the estimation of parameters characterizing formation properties such as permeability, for fluid flow monitoring, detection of fractures and fluid contacts. Much of the current activity is associated with dynamic measurements using acoustic stimulation of the formation to induce fluid motion by sonic or seismic means. For example, acoustic-electric coupling to measure permeability through electrokinetic effects is described in a 1957 patent, U.S. Pat. No. 2,974,273 entitled “Method and Apparatus for Investigating Earth Formations”, Vogel and Weiser (Shell).
Much of the current activity involves acoustic (either using downhole sonic sources or seismic techniques) excitation to generate electrokinetic effects. Recent examples are M. Charara and P. Ligneul, U.S. Pat. No. 7,148,693, Process and Device for Prospecting a Porous Geological Formation, and M. Charara and P. Ligneul, U.S. Patent Publication No. 2007/0150200A1, Characterizing Properties of a Geological Formation by Coupled Acoustic and Electromagnetic Measurements.
Of particular relevance is a 1984 patent by R. Chandler, U.S. Pat. No. 4,427,944 entitled “System for Permeability Logging by Measuring Streaming Potential”, which discloses the use of a test tool in conjunction with electrokinetic measurements said to have influenced the RFT (Repeat Formation Tester).
Other recent publications include:
Po-Zen Wong, U.S. Pat. No. 5,417,104, Determination of Permeability of Porous Media by Streaming Potential and Electro-osmotic Coefficients.
S. Garambois and M. Dietrich, Seismoelectric Wave Conversion in Porous Media: Field Measurements and Transfer Function Analysis, Geophysics 66(5) 2001, pp. 1417-1430.
Millar et al., U.S. Pat. No. 6,597,633, Method for Electrokinetic Downhole Logging.
Millar et al., U.S. Pat. No. 6,842,697, Method for Downhole Logging.
Kobayashi, Toshioka, Takahashi, Millar and Clarke, Development of Practical EKL (Electrokinetic Logging) System, SPWLA 43rd Logging Symposium, Jun. 2-5, 2002.